In general, a liquid of a semiconductor highly pure chemical, a general chemical, or the like is charged into a liquid storage container such as a polyethylene tank in a production plant, and shipped in a state that a lid is attached to a stopper portion formed in this liquid storage container for charging and taking out. As a method of taking out the liquid accommodated in such a liquid storage container, there is a known siphon method of introducing a gas such as the air into the container so as to feed the liquid to an exterior of the container by gas pressure thereof.
In this siphon method, after the lid attached to the stopper portion of the liquid storage container is detached, a plug provided with a siphon serving as a liquid flow passage and a gas flow passage is attached. After that, by connecting a socket capable of being respectively coupled to a tube for taking out the liquid to the exterior of the liquid storage container and a tube for introducing the gas into the container to the plug, the liquid flow passage for taking out the liquid and the gas flow passage for introducing the gas are formed.
For example, as disclosed in the Publication of Japanese Patent No. 4713676, there is a liquid storage container adopting a double structure in which a flexible container accommodating a liquid is installed in an outer container. In such a liquid storage container having a double structure, the flexible container pushes out the inside liquid upon receiving external pressure. Thus, an amount (remaining amount) of the liquid which is left on a bottom surface of the container so as not to be taken out can be reduced.
In a conventional example of the liquid storage container having the double structure shown in FIG. 7, a liquid storage container 1 has a double structure provided with a flexible liner (flexible container) 2 and an outer container 3, and a plug 10 provided with a siphon 30 is attached to a stopper portion 4 of the outer container 3. At the time of taking out a liquid from the liquid storage container 1, a socket 50 is coupled to the plug 10, gas pressure (arrow P in the figure) is introduced into the outer container 3, and the liner 2 is pressed from the outside, so that the liquid accommodated in the liner 2 flows out to an exterior of the container from an ejection port 31 formed on the lower end side of the siphon 30 which is inserted into the liner 2 as if the liquid is pushed out. It should be noted that the reference sign 5 in the figure denotes a liner bracket to which the liner 2 is welded and attached.